It has been traditional to line heated vessels such as soaking pit covers with dense fire brick linings. Such linings however, are sensitive to thermal shock which can severely limit the lifetime of the lining. It has therefore been more recently proposed to line soaking pit covers with fibrous refractory insulating materials. For example, it has been proposed in U.S. Pat. No. 3,854,262 to arrange strips of ceramic fiber blankets into compressed panels by means of metallic parts buried in the blanket material exerting compressive pressure on the material. At the portion of the panel away from this internally exerted compression, the fibrous blanket strips will tend to "blouse", so that on the furnace side of the soaking pit lid there will be a continuous protection of insulating material. Or the strips of fibrous insulation can be impaled on spikes, with the spikes projecting outwardly from under a top plate, on metal support members, of a soaking pit cover. Such structure has been shown and discussed in U.S. Pat. No. 3,853,077.
As opposed to such strips of fibrous blanket material, it has also been proposed to employ a series of interlocking U-shaped mats. By the interlocking of the mats of such shape, heat path leakage can be reduced or even eliminated. Such leakage across the more traditional fire brick linings tended to fracture the refractory brick and/or the mortared joints between the brick. The utility of such a structure for soaking pit covers has been discussed in U.S. Pat. No. 4,411,621. Therein, it has been more specifically shown to support the fibrous mats by securing them to a metal mesh cover, such as by wire ties.
Blocks of ceramic fiber blankets, having a somewhat squared off face, have also been used in soaking pit covers. These blocks, as shown for example in U.S. Pat. No. 4,449,345, have internal support structure and an external clip for fastening. Such clip may be fastened on to a mating element attached to a metal mesh cover. To compensate for fiber shrinkage during cover use, loose repair fiber can be manually wedged between blocks, from the hot face, while the cover is not in service.
More recently, in U.S. patent application Ser. No. 602,197, it has been proposed that a cover such as for a furnace or soaking pit contain a series of U-shaped blankets in side-by-side relationship. These blankets serve as the principle covering elements, and may be supported by hangers slideably engaging a support bar. By means of this structure, compression exerted against an end blanket can be transmitted across the covering of the blanket elements by virtue of the sliding hanger arrangement. Moreover, the hangers can be sized to provide for limiting the maximum degree of sliding, or compression, of the covering blankets.
It would, however, be most desirable to assemble a cover structure that overcomes the disadvantages of fire brick linings and offers the advantages of ceramic fiber insulation, while commensurately providing a structure not only of great ease of assembly, but also ease of repair. It would also be most desirable that such structure have the facility of blanket compression, without inducing deleterious degradation of fiber blanket integrity during compression. It would furthermore be advantageous if such cover structure was most lightweight and could be readily placed upon and removed from the soaking pit.